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From:   Josh Don <joshdon@google.com>
Date:   Mon, 23 Aug 2021 10:29:53 -0700
Message-ID: <CABk29NvH6_JoLydcrJf+yiaasGUbNEjzKdPjZxnWdrAFboJdsg@mail.gmail.com>
Subject: Re: [PATCH v3 1/4] sched: cgroup SCHED_IDLE support
To:     Tao Zhou <tao.zhou@linux.dev>
Cc:     Ingo Molnar <mingo@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Juri Lelli <juri.lelli@redhat.com>,
        Vincent Guittot <vincent.guittot@linaro.org>,
        Dietmar Eggemann <dietmar.eggemann@arm.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
        Daniel Bristot de Oliveira <bristot@redhat.com>,
        Paul Turner <pjt@google.com>,
        Oleg Rombakh <olegrom@google.com>,
        Viresh Kumar <viresh.kumar@linaro.org>,
        Steve Sistare <steven.sistare@oracle.com>,
        Tejun Heo <tj@kernel.org>, Rik van Riel <riel@surriel.com>,
        linux-kernel <linux-kernel@vger.kernel.org>
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Precedence: bulk

Hi Tao,

On Fri, Aug 20, 2021 at 1:38 AM Tao Zhou <tao.zhou@linux.dev> wrote:
[snip]
> >  #ifdef CONFIG_SMP
> >  extern void set_task_rq_fair(struct sched_entity *se,
> >                            struct cfs_rq *prev, struct cfs_rq *next);
> > @@ -601,6 +606,9 @@ struct cfs_rq {
> >       struct list_head        leaf_cfs_rq_list;
> >       struct task_group       *tg;    /* group that "owns" this runqueue */
> >
> > +     /* Locally cached copy of our task_group's idle value */
> > +     int                     idle;
> > +
> >  #ifdef CONFIG_CFS_BANDWIDTH
> >       int                     runtime_enabled;
> >       s64                     runtime_remaining;
> > --
> > 2.33.0.rc2.250.ged5fa647cd-goog
> >
>
> Cfs_rq and tg define @idle with int type.
> In sched_group_set_idle(..., long idle), @idle is long type.
> Use int instead.
>
> But, you filter idle value:
>
>     if (idle < 0 || idle > 1)
>         return -EINVAL;
>
> So, no effect here.. Just @idle can use 4 bytes.
>
>
>
> Thanks,
> Tao

The use of 'long'  there is because the input from the cgroup
interface is a 64 bit value.

- Josh